Cupola furnace



H. P. KREULEN CUPOLA FURNACE Filed July 3, 1947 Herman r? reu/en Patented Jan. 24, 1950 iJNlTED STATES PATENT OFFICE CUPOLA FURNACE Herman P. Kreulen, Elm Grove, Wis., assignor to Grede Foundries, Inc., Milwaukee, Wis., a corporatio'n of Wisconsin Application July 3,1947,- Serial No. 758,924

5 Claims. (01. 266-30) This invention relates to improvements in cupola furnaces.

. It is the object of the invention to reduce any tendency for bridging to 'occur in the cupola, to enable cupola operation at higher temperatures, to increase the melting capacity of a cupola of given size, to materially reduce the time required to knock out the slag, and to effect substantial savings of refractory material. The manner in which these objectives are achieved will appear more fully from the following disclosure of the invention.

9 In the drawings:

Fig. 1 is a view in side elevation of a cupola furnace embodying the invention.

Fig. 2 is an enlarged, fragmentary detail view partially in side elevation and partially in section through the portion of thecupola with which the present invention is concerned.

Fig. 3 is aviewtaken in horizontal section on line 3-3 of Fig. 2.

Fig. i is a further enlarged detail view in perspective showing component parts of the tuyre.

The cupola shell 5 and its support on a base 6 carried by columns I are generally conventional. The base is provided with theusual bot tom trap doors shown closed in Fig. 2, and one of'which is shown open in Fig. 1. Mounted on the shell is a conventional wind box 9 supplied with air under pressure bythe usual blower (not shown). The windbox serves as a manifold to distribute the air to the various tuyre openings through the knees l0.

The interior of the shell has a refractory lining l i, through the lower portion of which opens the tap spout l2 and, at a slightly higher level, the slag spout I3. At a predetermined level, a few inches above the slag spout, are the tuyere blocks !5. These blocks are so flared as to increase in cross section in an inward direction. As shown in Fig. 4, the sides and bottom are preferably made'integral, and the top segment I6 is separately fabricated. There is usually an intermediate baflie or partition 11. The tuyere blocks are symmetrically disposed, and the openings therethrough afford communication between the knees in and the interior of the cupola for delivering the blast to the charge.

Immediately above the tuyeres, the lining is preferably increased in thickness or boshed at It to provide an overhang which tends to exclude both cok and slag from the tuyere openings. The boshed section is gradually tapered at l9 back to the original interior cross sectional dimension at 20.

The operation of my cu'pola follows generally the accepted practices. The trap doors 8 are closed and covered with a filling of dry sand to provide a bottom which drains toward the tap opening 42. Kindling on the sand is sufficient in amount and distribution to ignite the coke. About a third of the initial charge of coke is placed on the kindling and thoroughly ignited before the rest is added and before the blast is started. After the first batch of coke is thoroughly ignited, the second is introduced onto it, and when this is in full ignition, the third batch is added. Thereupon, the furnace is charged with iron and coke in the usual manner, and the blast is set in operation by supplying air under pressure to the windbox.

.When the level of molten iron reaches a point where slag appears at the slag spout 13, the tap spout is opened, and the molten iron drained off until slag appears, whereupon it is again closed.

After all of the molten iron has been withdrawn at the conclusion of the heat, the trap.

doors 8 are opened to dump the residue of coke and slag. After the cupola is cool, and before any relining can be done, iron and slag adhering to the refractory lining must be broken out. In some instances, there is such adhesion of the sla and molten iron to the lining as to result in hanging up, the entire mass bridging across the. interior of the :cupola and failing to discharge through the trap doors 8. The present invention minimizes adhesion of the iron orslag to the lining and substantially completely prevents hanging up, assuring a clean drop when the trap doors are opened. These results are brought about by using certain proportions which I have discovered.

. In the past, there has been no recognised relationship between the tuyere size and the size of the cupola. The average cup'ola, regardless of size; has had tuye're openings which, as measured atthe exterior shell, were about 5% or 6 inches high, and of :sufiicient area to amount to a maximum of 25% of the horizontal cross section of the eupola. That is to say, the aggregate vertical cross sectional area of all of the tuyere openings totaled only a quarter the horifontal cross section of the cupola at the tuyere e'vel.

have discovered, and have demonstrated in actual commercial production, that remarkable and unexpected improvements in the functioning of the cupola are achievable provided the tuyere openings have an aggregate cross section of at least approximately /3, and preferably at least 35% of the horizontal cross section of the cupola at tuyere level, and provided further that, re gardless or" cupola dimensions, the minimum height of the tuyere opening should be at least nine inches, and preferably approximately 11 inches. the specified height and the specified minimum cross section are essential. The results do not follow from the use of the specified minimum cross section unless the minimum height is stated. Neither are the results 012- tainable in the use of the specified minimum height unless the area also bears the requisite relation to cupola cross section. Since the tuyeres ordinarily flare inwardly,-both the height and tuyre a referred to are ordinarily measured at The po e variation in height is such that a height as low as 9 inches may siully. A, tuyere of less than 9 nt is not desirable, regardless of ileit is known that some tuyres on as 9 inches, or even 11 inches, are none to my knowledge which nts of 9 to 11 inches or more in c i. '11 an area of anywhere nearly that of the horizontal cross section of the cupola. Both the relative area and the height are requirec for the desired result.

There are many published recommendations as to the tive size of tuyere openings. I am 'Ln a number of these, and they all tuyere openings of a size very substantially smaller than. that which I have found to give the unexpected results which are achieved through the use of my invention.

These 1 ults are believed to be attributable in part to the fact that the specified relative area or" the tuyeres is such as to reduce the the air blast at the tuyere openings. velocity is high, the air tends to follow channels through the charge. ate proximity to the path of the air, the molten iron and slag are unduly cooled and caused to congeal and adhere to the fire brick or other "efractory which lines the cupola. In cases, this results in bridging, which precludes the desired clean drop when the trap doors are opened. In all cases, the adhesion of the slag and iron to the fire brick increases the time req d to clean out the cupola. It also results in my to, or destruction of, the fire brick or th-: refractory material.

Where the specified dimensions and proportions are followed, bridging is so far reduced as to be substantially eliminated, even though the melting be conducted at higher temperatures with consequent increase in relative output. The melting capacity has been so greatly increased that it is common to find an increase of 15% in output as compared with the output of a cupola of the same size but with conventional tuyres.

The time required to knock out the material ad duced to f, or less than half, of the time required to knock out a conventional cupola of otherwise identical design. In many respects, the knock out time has been reduced to as low as /5 of the time required to knock out" the same identical cupola before the tuyeres thereof were changed in accordance with the present invention.

Along with the saving in knock out time goes a substantially equivalent saving in fire brick or refractory lining material.

I claim:

1. .A cupola having tuyere openings the mini mum dimensions of which comprise a height of at least nine inches, and an aggregate cross section of at least one-third the area of the horizontal interior cross section of the cupola at the level of the tuyrere openings.

2. A cupola having a shell and a refractory lining, with tuyre openings through the shell and lining which flare inwardly and have a minimum opening adjacent the shell of eleven inches in. height, said tuyere openings having an aggregate area at their minimum cross section of at least one-third the cross sectional area of the interior of the cupola lining at the level of such openings.

3. A cupola having a shell and refractory lining and provided with tuyre openings through the shell and lining flaring inwardly from the shell, said openings having a minimum height of nine inches and a minimum aggregate cross sectional area equal to at least 35% of the horizontal cross sectional area of the interior of the cupola lining at the level of such openings.

4. In a cupola having a shell, a windbox, and a refractory lining, a plurality of tuyere blocks built into the lining and opening into the cupola and externally communicating with the windboX, each such block flaring inwardly from the shell and having a minimum height of eleven inches, the aggregate total cross section of the minimum cross sectional areas of the openings through said blocks being at least thirty-five per cent of the total horizontal cross sectional area of the interior of the cupola lining at the level of such openings.

5. In a cupola furnace comprising a support provided with trap doors, a shell upstanding on said support, a windbox encircling the shell, knees leading from the Windbox and a refractory lining for the shell, the lining and shell having tuyere openings with which said knees communicate, the combination of tuyere blocks extending through the lining from the shell, said lining having an overhang above the blocks, the blocks having a minimum height in excess of nine inches and an aggregate minimum cross sectional area at the shell totalling at least onethird of the horizontal cross sectional area of the cupola at the level of said openings.

HERMAN P. KREULEN.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PAIJLNTS Number I Name Date 324,623 Whiting Aug. 18, 1885 1,279,446 Boss Sept. 17, 1918 2,112,908 Hamilton A131. 5, 1938 OTHER REFERENCES Moldenke: The Principles of Iron Founding, published 1930, by McGraw-Hill Book Company, Inc., New York and London, pages 421-427. 

